Technical Field
The present invention relates to a flange fixing structure, and in particular to a flange fixing structure which is suitable for fixing and sealing a flange part when the temperature variation is significant.
Background Art
As a method of connecting a plurality of pipe conduits in a serial manner, there is a method in which a flange part is provided at an end part of a pipe conduit and flange parts of two pipe conduits are fixed with each other in a butting manner via a gasket. Such method of fixing flange parts is defined in many standards, including Japan Industrial Standards (JIS)-B2220, and is widely and generally used (see, for example, JP2013-234734 A and JP2010-133493 A).
In order to prevent the leakage of a fluid passing through pipe conduits, it is necessary to apply an appropriate surface pressure to the gasket so as to fix the flange parts. In such case, even when an appropriate surface pressure is applied at the time of assembly, if deficiency in surface pressure occurs during use, a leakage of fluid will occur.
Causes of surface pressure deficiency include the expansion of flange fixtures due to temperature variation, plastic deformation of such flange fixtures and gaskets, or the like. In particular, it is difficult to keep the fluid sealed in by means of flanges for a long period of time at locations where the temperature variation is significant.